1. Field of the Invention
The present invention relates to a signal processing device and the like, and particularly to a signal processing device that processes a signal from a sensor and forwards the signal to a control device and the like.
2. Description of Related Art
A signal processing device is known to acquire physical quantity detected by a sensor installed in an industrial machine such as a metering device from the sensor, perform signal processing on an acquired detection signal, and forward the detection signal to a control device that controls the industrial machine. In the signal processing device, an analog signal acquired from the sensor is amplified, is converted to a digital signal by using an analog/digital (A/D) converter and forwarded to the control device. Moreover, the signal processing device removes noise from the digital signal through a digital filter and sends the digital signal to the control device.
In a control system including the signal processing device, there are a variety of metering objects (generally referred as works) metered by the metering device, and noise generated corresponding to the metering objects may also vary. Therefore, the noise that should be removed in the signal processing device is not necessarily the same, and the frequency of the noise that should be removed has to set corresponding to the metering objects each time.
In addition, for example, a technology is disclosed in Patent Document 1, that is, in the metering device, a rotational speed signal of a motor is used as a basic frequency, and generation of an abnormal state is judged by using amplitude of a particular frequency calculated by multiplying the basic frequency by multiplying power. According to the technology, the abnormal state can be judged by using the rotational speed signal of the motor, and thus the abnormal state can be judged easily even if the metering objects change.